The present invention relates to a microphone test procedure, specifically to a microphone test procedure for calibrating the sensitivity of a microphone.
In order to take detailed measurements with a microphone, its precise sensitivity must be known. Since this may change over the lifetime of the device, it is necessary to regularly calibrate measurement microphones. A microphone's sensitivity varies with frequency (as well as with other factors such as environmental conditions) and is therefore normally recorded as several sensitivity values, each for a specific frequency band. A microphone's sensitivity can also depend on the nature of the sound field it is exposed to. For this reason, microphones are often calibrated in more than one sound field, for example a pressure field and a free field.
Microphone calibration services are offered by some microphone manufacturers and by independent certified testing labs. The calibration techniques carried out at designated microphone calibration sites often involve multiple additional microphones in order to calibrate a single device. All microphone calibration is ultimately traceable to primary standards at a National Measurement Institute, such as NIST in the U.S. The reciprocity calibration technique is the recognized international standard with regard to microphone calibration and testing procedures.